The pathophysiology of constipation in the setting of longstanding diabetes mellitus is not well understood. We have found that acute hyperglycemia blunts the perception of rectal distention in healthy volunteers without altering rectal compliance or peripheral afferent neural function between the rectum and cortical structures. In the current study, we plan to use PET scanning to localize the forebrain and brainstem structures active during the perception of rectal stimulation. We will further evaluate the effect of acute hyperglycemia on the activation of these structures.